Devices of said type are sufficiently well known in the prior art. For example, U.S. Pat. No. 6,484,678 B2 describes a solution in which an inner rotor is screwed by means of a central screw to the camshaft of the internal combustion engine. The outer rotor is operatively connected by means of a chain or by means of a toothed belt to the crankshaft, and is mounted on the inner rotor so as to be rotatable with respect to the latter. In addition, the outer rotor is provided with cheeks which are spaced apart in the peripheral direction and which extend inward from a radially inner peripheral face of the outer rotor. The radially inner delimiting faces of the cheeks bear against the inner rotor and therefore serve as bearing faces. In addition, the cheeks serve to define recesses on the outer rotor, which recesses are closed off in a pressure-tight manner by means of the inner rotor and two side walls and therefore serve as hydraulic chambers. A relative rotational movement can—in a manner controlled by means of an external hydraulic load—be initiated between the inner rotor and the outer rotor. For this purpose, the inner rotor is embodied as a vane wheel which is composed of a hub part and vanes which are formed in one piece with said hub. The vanes adjoin the outer peripheral face of the hub part and extend outward in the radial direction. In addition, each vane engages into a hydraulic chamber and divides the latter into two pressure chambers which act counter to one another. By means of corresponding loading of the respective pressure chamber, it is possible for an adjustment of the inner rotor relative to the outer rotor to take place between an “early stop” and a “late stop”.
A further embodiment of devices of said type is described for example in DE 198 08 618 A1, in DE 199 51 391 A1 and in DE 102 53 496 A1. Here, in contrast to the first embodiment the vane(s) and the hub part of the inner rotor are produced separately. The vanes are arranged in vane grooves which are formed on the outer lateral surface of the hub part. In each case one vane divides a hydraulic chamber into two pressure chambers which act counter to one another. By means of corresponding loading of the respective section of the hydraulic chamber, it is possible for an adjustment of the inner rotor relative to the outer rotor to take place between an “early stop” and a “late stop”. As an alternative to said embodiment, it is likewise possible to form the vane grooves into an inner lateral surface of the outer rotor, and to arrange the vanes there.
In order to ensure that the vanes are pressed radially outward against the radially outer end of the hydraulic chamber, in order to thereby sealingly delimit the two sections of the hydraulic chamber by means of the vane, it is known from DE 199 63 094 A1, from DE 198 08 619 A1 and from DE 199 14 047 A1 to arrange a leaf spring element in the vane groove base of the vane grooves which support the vanes, which leaf spring element exerts a radially outwardly aligned force on the vanes.
One problem of said devices is the fact that relatively high leakage flows flow between the pressure chambers of a hydraulic chamber or opposing pressure chambers of adjacent hydraulic chambers. Here, the oil passes from the oil chamber in which the higher pressure prevails to the respective pressure chamber in which the lower pressure prevails via the gap between the vane and the outer rotor or via the gap between the inner rotor and the outer rotor in the region of the bearing points.
Although a reduction in size of the gaps leads to a reduced degree of leakage, it brings with it increased friction and increased production costs on account of narrower tolerances and therefore higher production expenditure.
A solution to said problem is described in U.S. Pat. No. 6,484,678. Radial grooves which run substantially in the axial direction are formed on the radially outer face of the vanes and in the region of the bearing faces of the outer rotor. Arranged in the grooves are sealing strips which are pressed by means of spring elements against the opposing face of the in each case other component. The spring elements are supported at one side on the groove base of the grooves and at the other side against the sealing strip. The gaps between the inner rotor and the outer rotor are therefore closed off, and the leakage is reduced.
Although it is already possible with a solution of said type to obtain a good efficiency of the arrangement, leakage losses, like before, represent a problem of such devices. Said leakage is caused inter alia in that hydraulic fluid infiltrates from the one pressure chamber into the groove which supports the sealing strip, and passes via the groove base to the other pressure chamber. Especially in applications in which high reaction torques act on the camshaft, said leakage paths lead to unstable phase positions between the camshaft and the crankshaft.
The leakage behaviour is an important quality criterion of a device of said type, since this co-determines the size, that is to say the installation space and the weight, of the adjuster, and as a result also influences the design of the valves, oil pumps etc.
A disadvantage of the previously known solutions is that, in the central position of the phase position, an increased degree of leakage occurs in the groove; the sealing strip is subjected there to an alternating pressure loading between the two regions of the hydraulic chamber. This generates an alternating tilting movement of the sealing strip in the groove, which can lead to increased leakage. In the case in particular of a plurality of hydraulic chambers and vanes, the leakage losses add up here to a considerable order of magnitude.
Although the reduction in the internal leakage can be obtained by means of narrower tolerancing of the grooves and sealing strips or by means of higher friction coefficients in the leakage gap, the production accuracy required here however results in considerably higher production costs, for which reason this is no practicable approach for significantly improving the leakage behaviour, in particular the internal leakage behaviour, of the adjuster. Costs are also driven up by additional sealing elements which also disadvantageously increase the weight of the adjuster.